Wheel suspension

ABSTRACT

A wheel suspension includes an axle limb which supports a wheel. The axle limb includes a first steering axle which provides a first steering angle in a specified range for the wheel, and components for connecting the axle limb to a support structure. At least one of the components includes a second steering axle which provides a second steering angle which is different than the first steering angle provided by the first steering axle. The second steering axle is selectively releasable. The components for connecting the axle limb to the support structure form a double transverse link axle which includes an upper traverse link and a lower traverse link. A support tube is arranged at a chassis-side end portion of each of the upper traverse link and the lower traverse link of the double transverse link axle. The support tube is pivotable about the second steering axle.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2018/053333, filed on Feb. 9,2018 and which claims benefit to German Patent Application No. 10 2017106 810.4, filed on Mar. 29, 2017. The International Application waspublished in German on Oct. 4, 2018 as WO 2018/177642 A1 under PCTArticle 21(2).

FIELD

The present invention relates to a wheel suspension, in particular for avehicle body, comprising an axle limb which supports a wheel and havinga first steering axle for the wheel, the first steering axle allowing asteering angle in a specified range, and comprising components forconnecting the axle limb to a support structure.

BACKGROUND

Standard vehicle bodies are currently predominantly used in automotivetechnology whose individual geometry is based on the specific loadrequirements of the respective vehicle model.

Known wheel suspensions for personal and utility vehicles include thefollowing:

-   -   McPherson, wheel-guiding suspension strut with additional single        or double transverse links (optional wishbone suspension links)        as a large base or a small base    -   Multi-link axle    -   Composite steering arm or coupling link axle    -   Trailing arm and rigid axles

Only one axle, i.e., the front axle, is normally steered; rear axles arepartially designed to be co-steered but are rarely used in practice. Anactively steering rear axle that enables a large steering angle similarto the front axle is to be found only in custom solutions and not inlarge series production. The maximum possible steering angle at thefront axle is limited by the geometry of the selected wheel suspension.

A disadvantage of the limited steering angle of known wheel suspensionsis, for example, that a vehicle parked parallel to a road requires arelatively large parking space for maneuvering, and the utilization ofavailable parking space, which is becoming more and more limited, istherefore not optimal. Traffic flow is also impeded or stopped by theusually required reverse parking. A vehicle also cannot rotate on apoint. A turning circle measures between 9 and 13 meters in diameterdepending on vehicle class.

SUMMARY

An aspect of the present invention is to provide a suitable drivingmechanism geometry which reduces the parking space required for vehiclesand to achieve a largely exact, space-saving, and automated parking atright angles and with only a minimal hindrance of traffic.

In an embodiment, the present invention provides a wheel suspensionwhich includes an axle limb which is configured to support a wheel. Theaxle limb comprises a first steering axle which is configured to providea first steering angle in a specified range for the wheel, andcomponents for connecting the axle limb to a support structure. At leastone of the components comprises a second steering axle which isconfigured to provide a second steering angle which is different thanthe first steering angle provided by the first steering axle. The secondsteering axle is configured to be selectively releasable. The componentsfor connecting the axle limb to the support structure form a doubletransverse link axle which comprises an upper traverse link and a lowertraverse link. A support tube is arranged at a chassis-side end portionof each of the upper traverse link and the lower traverse link of thedouble transverse link axle. The support tube is configured to bepivotable about the second steering axle.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basisof embodiments and of the drawings in which:

FIG. 1 shows a first exemplary embodiment of a wheel suspension withdouble transverse links in a perspective view;

FIG. 2 shows the wheel suspension according to FIG. 1 in a perspectiveview rotated by 90°;

FIG. 3 shows the wheel suspension according to FIG. 1 from above wherethe wheel is in a position pointing straight ahead in the direction oftravel;

FIG. 4 shows the wheel suspension according to FIG. 1 from above wherethe wheel has a maximum steering angle of about 40° about the firststeering axle;

FIG. 5 shows the wheel suspension according to FIG. 1 from above wherethe wheel has an angle of approximately 90° with respect to thelongitudinal axis of the vehicle;

FIG. 6 shows a schematic side view of the wheel suspension deviceaccording to FIG. 1;

FIG. 7 shows a view from above of an alternative embodiment of a wheelsuspension with double transverse links where the wheel is straight inthe direction of travel;

FIG. 8 shows a view from above of an alternative embodiment of a wheelsuspension with double transverse links where the wheel is pivoted aboutthe first steering axle;

FIG. 9 shows a view from above of an alternative embodiment of a wheelsuspension with double transverse links where the wheel is pivoted bothabout the first steering axle and the second steering axle and is at anangle of approximately 90° to the longitudinal axis of the vehicle;

FIG. 10 shows a schematic side view of the wheel suspension according toFIGS. 7 to 9;

FIG. 11 shows a schematic side view of a McPherson wheel suspension; and

FIG. 12 shows a schematic side view of an alternative McPherson wheelsuspension.

DETAILED DESCRIPTION

The basic concept of the present invention is to adjust thewheel-specific steering angle to 90° (or more) to the right and to theleft by integrating an additional second steering axle into aconventional steering wheel suspension between the rotary bearing of anaxle limb and the connection of the wheel suspension to the vehicle ortransport means. According to the present invention, at least one of thecomponents has a selectively releasable second steering axle in order toproduce a steering angle other than the one defined by the firststeering axle.

Even if the present invention is described below on the basis of avehicle body, the field of application of the present invention is notrestricted thereto. In addition to being used in vehicle engineering,the solution of the present invention can also be implemented in anyother mobile application. A use is, for example, generally conceivablein the transport of goods or persons. As examples, mention should herebe made in particular to utility vehicles and transport means fordisabled persons or vehicles for logistics in special environments suchas, for example, storage spaces. Vehicles can also be used in interiorspaces and have special structures such as a flexible lifting crane, afork lift, a conveyor belt transporter (the body being transported onthe vehicle), and the like.

In a pure driving mode of a vehicle, the vehicle is guidedconventionally by fine rotational movements of the outer axle limbassigned to the steering axle (about 40° steering angle in bothdirections). For parking or transverse driving at lower speeds, thesecond, inner, i.e., body-side, steering axle is unlocked from itsdriving position and increases the total steering angle by superimposingthe angles of rotation of both axles up to a wheel angle transverse tothe longitudinal direction of the vehicle.

This type of wheel suspension can be used not only for the front axle,but also for all other vehicle axles (all-wheel steering). Control ofthe steering system via the second, inner steering axle can be exertedboth on the individual wheel suspension (single-wheel steering viacorresponding actuators) and via steering kinematics which couples bothwheels of an axle and is driven by only one actuator.

Enabling a steering angle of up to 90° or more in both directions via anadditional, inner steering axle offers two essential advantages:

-   -   The steering roll radius (distance of wheel contact point to a        theoretical point of intersection of the outer steering axle and        roadway) can be designed to be small or even zero; the influence        of driving or braking torque on steering in the driving mode is        thus very low.    -   By suitable selection of the position of the second, inner        steering axle, the wheel rotates into the wheelhouse parallel to        the transverse link in the smallest possible space; the wheel        opening need not be increased, which results in a space-saving        arrangement and more design freedom.

In addition to a conventional steerable axle (for example, multiplelinks, double transverse link, McPherson strut suspension, pendulumaxle, longitudinal link axle), in an embodiment of the presentinvention, a further joint having six degrees of freedom (for example, asupporting joint) can, for example, be introduced between the rotarybearing of the axle limb and the connection of the wheel suspension tothe vehicle or transport means, thus dividing the transverse link intoan outer short and an inner long transverse link. The bearing of thefirst, outer steering axle is replaced by a purely rotary bearing (forexample, a tapered roller bearing). In addition to rotation about thesecond, inner axle, the bearing between a short and a long transverselink assumes the task of a wheel suspension and therefore must beequipped with six degrees of freedom.

Implementation in a double wishbone axle is accomplished by integratingthe upper and lower short wishbone links or coupling them as a unit viaa connector. The spring damper unit is rotatably mounted on the inner,long wishbone link and is supported directly on the body.

Implementation in a McPherson strut suspension takes place analogouslyto the double wishbone axle, with only the lower wishbone link beingdivided. The upper point of the second, inner steering axle is thearticulation point between the suspension strut and the body.

In an embodiment of the present invention, an actuator for rotating thewheel about the first steering axle can, for example, be arranged on theaxle limb. The actuator can be designed as an electric motor or as ahydraulic or pneumatic unit. The mechanically very complex transmissionof steering commands via a conventional steering gear can thus beavoided.

In an embodiment of the present invention, the components for connectingthe axle limb to the support structure can, for example, be designed asa double wishbone axle. In this case, a support for the axle limb isadvantageously provided, which is arranged pivotably about the secondsteering axle on an upper and on a lower wishbone link of the doublewishbone axle. Alternatively, a support tube for the wishbone links,said support tube being pivotable about the second steering axle, can bearranged on end regions of an upper and a lower wishbone link of thedouble wishbone link on the side of the support structure.

In an embodiment of the present invention, the components for connectingthe axle limb to the support structure are designed as a McPherson axle.

Since the second steering axle can, for example, not be used in normaldriving operation at higher speeds, it can, for example, have a lockingmechanism which can be released via a mechanical, electrical, hydraulic,or pneumatic actuating element.

Since the transmission of drive forces to the wheel in the suspensionaccording to the present invention would be very complicatedmechanically, a wheel hub motor can, for example, be arranged as a driveon the wheel.

In an embodiment of the present invention, the suspension of the presentinvention allows additional or alternative functions and applications:

-   -   Elimination of the steering actuator on the inner axle: the        upper short transverse link is omitted. By locking and opening        the lower intermediate joint, the additionally required steering        angle of 90° relative to the driving direction can be        accomplished by the wheel drive only.    -   Reduction of track width: by an equally dimensioned but opposite        steering angle of both steering axles (40° to the left for the        outer axle, 40° to the right for the inner axle), the steering        effect is magnified while the track width is reduced.    -   Redundant brake/emergency braking: in some circumstances, an        additional mechanical brake can be dispensed with or brake        failure can be compensated by the steering system. Service        braking is accomplished via the wheel hub motor (recuperation        brake); emergency braking is additionally supported by an        adjustment of the wheels in the toe-in. Or in the event of        failure of the brake, a braking torque is generated by a mutual        steering of the wheels.    -   Forces and torques are measured on the bearing of the inner axis        of rotation, and the forces and torques on the wheel are deduced        from these measurements. With the aid of evaluation electronics,        operating cases, load spectra, roadway conditions, tire        characteristics, and the coefficient of friction are determined        as relevant vehicle characteristics.

The present invention will be explained in more detail below underreference to an embodiment shown schematically in the drawings.

The wheel suspension illustrated in FIGS. 1 and 2 essentially comprisesa wheel 10 with a wheel carrier 12 which is designed as a wheel hubmotor, having an axle limb 14 carrying the wheel and having a firststeering axle 16 (FIG. 6), a support 18 for the axle limb 16, an upperwishbone/triangular transverse link 20, a lower wishbone/triangulartraverse link 22, an actuator 24 arranged on the axle limb 14 forsteering the wheel 10 about the first steering axle 16, tapered rollerbearings 26, 26′ arranged at the top and at the bottom between the axlelimb 14 and the support 18, a link 28 for rotating the support 18 abouta second steering axle 30 (FIG. 6), a spring-damper unit 32, a lockingmechanism 34 for locking the second steering axle 30 in the drivingmode, and support bearings 36, 36′ (FIG. 6) arranged at the top and atthe bottom between the support 18 and the wishbone/triangular traverselinks 20, 22. A vehicle chassis is symbolically indicated by struts 38,38′, on which the upper and lower wishbone/triangular traverse links 20,22 are pivotably fastened. In FIGS. 1 and 2, the wheel 10 is rotatedboth about the first steering axle 16 and the second steering axle 30 sothat a total steering angle of approximately 90° with respect to thelongitudinal direction of the vehicle is achieved. If all availablewheels are steered in such a way, a vehicle can be moved transversely toa road, such as for parking.

FIG. 3 shows the wheel 10 in a position pointing straight ahead in thedirection of travel. FIG. 4 shows the wheel 10 with a maximum steeringangle of about 40° about the first steering axle 16, for example, duringcornering. The second steering axle is here locked. FIG. 5 shows thewheel 10 at an angle of approximately 90° with respect to thelongitudinal axis of the vehicle. The second steering axle 30 isunlocked in this case and its rotational angle adds to the rotationalangle of the first steering axle 16.

FIGS. 7 to 9 show a plan view of an embodiment of a double transverselink axle in which, instead of a support 18 for the axle limb 14 (FIGS.1 to 6), a support tube 40 arranged on the chassis-side ends of theupper and lower transverse links 42, 44 contains the second steeringaxle 30. FIGS. 7 to 9 correspond to FIGS. 3 to 5, respectively, of thefirst embodiment. In FIG. 7, the wheel 10 is straight in the directionof travel, in FIG. 8, the wheel 10 is pivoted about the first steeringaxle 16, and in FIG. 9, the wheel 10 is pivoted both about the firststeering axle 16 and second steering axle 30 and is at an angle ofapproximately 90° to the longitudinal axis of the vehicle.

FIG. 10 shows a schematic side view of the embodiment illustrated inFIGS. 7 to 9, in accordance with FIG. 6. Identical parts are hereprovided with the same reference numerals. The difference here isessentially the use of the support tube 40 as a support for the upperand lower transverse links 42, 44. The second steering axle 30 runsclose to the vehicle chassis through the support tube 40. To the extentthat no impeding vehicle components are in the way, this embodimenttheoretically permits a steering rotation of the wheel by 360°.

FIG. 11 shows a first embodiment of a McPherson wheel suspension in aschematic side view according to FIGS. 6 and 10. This wheel suspensionessentially comprises the wheel 10 with the wheel carrier 12, an axlelimb 46, a lower transverse link 48, an actuator 50 for rotating thewheel 10 about a first steering axle 52, a short link 54 as the lowerintermediate piece, a spring-damper unit 56, a locking mechanism 58 forlocking the second steering axle 60, and a link 62 for rotating thewheel 10 about the second steering axle 60.

FIG. 12 shows a second embodiment of a McPherson wheel suspension inschematic side view according to FIGS. 6, 10, and 11. The first steeringaxle 64 here runs through a support tube 68 arranged on an axle limb 66.The second steering axle 70 extends through the upper linkage of thespring-damper unit 56 and a support bearing 72 of a lower transverselink 74. The second steering axle can be locked by a locking mechanism76. The steering rotation of the wheel 10 about the first steering axle64 takes place via a linear actuator 78. The second steering axle 70 isarticulated via an upper link 80.

The following should be noted in summary: the present invention relatesto a wheel suspension, in particular for a vehicle body, comprising anaxle limb 14, 46, 66 which supports a wheel 10 and having a firststeering axle 16, 52, 64 for the wheel 10, the first steering axle 16,52, 64 allowing a steering angle in a specified range, and comprisingcomponents 18, 20, 22; 40, 42, 44; 48, 56; 56, 74 for connecting theaxle limb 14, 46, 66 to a support structure 38, 38′. In order to allow asteering angle of 90° or more to be reached, at least one of thecomponents 18, 20, 22; 40, 42, 44; 48, 56; 56, 74 has a selectivelyreleasable second steering axle 30, 60, 70 in order to produce asteering angle other than the one defined by the first steering axle 16,52, 64.

The present invention is not limited to embodiments described herein;reference should be had to the appended claims.

What is claimed is:
 1. A wheel suspension comprising: an axle limb whichis configured to support a wheel, the axle limb comprising, a firststeering axis which is configured to provide a first steering angle in aspecified range for the wheel, and components for connecting the axlelimb to a support structure; and a support tube, wherein, at least oneof the components comprises a second steering axis which is configuredto provide a second steering angle which is different than the firststeering angle provided by the first steering axis, the second steeringaxis is configured to be selectively releasable, the components forconnecting the axle limb to the support structure form a doubletransverse link axle which comprises an upper transverse link and alower transverse link, the support tube is arranged at a chassis-sideend portion of each of the upper transverse link and the lowertransverse link of the double transverse link axle, the support tubebeing configured to be pivotable about the second steering axis, and alongitudinal axis of the support tube defines the second steering axisso that the support tube is simultaneously pivotable both about thesecond steering axis and about the longitudinal axis of the supporttube.
 2. The wheel suspension as recited in claim 1, wherein the wheelsuspension is for a vehicle body.
 3. The wheel suspension as recited inclaim 1, further comprising: an actuator arranged on the axle limb, theactuator being configured to rotate the wheel about the first steeringaxis.
 4. The wheel suspension as recited in claim 3, wherein theactuator is an electric motor, a hydraulic unit, or a pneumatic unit. 5.The wheel suspension as recited in claim 1, wherein a wheel hub motor isarranged on the wheel as a drive.